This is an extraordinary milestone. The so-called "nones" now make up 22.8 percent of the nation while the percent of Catholics has fallen to 20.8 percent.

Thirteen percent of the U.S. population is now ex-Catholics* -- people who were raised Catholic and now identify as something else. If they were still Catholic, church members would make up over one-third of the nation.

Nor does the future look good for religion: The young are more likely to be nones than the old. About 35 percent of millennials say they do not belong to any religion, as opposed to only 17 percent of baby boomers. If the millennials and future generations stay unaffiliated for the rest of their lives, this will have a huge impact on churches and America.

Many hope that the young will return to the fold as they age, get married, and have children. Certainly, some will return to religion, but don't expect a mass migration back to church. Social scientists argue that the religious patterns that are set in people's 20s continue, for most of them, for the rest of their lives.

But before the churches despair, they need to take a closer look at these nones.

Who are the nones? The nones tend to be white (68 percent) and male (57 percent); 72 percent are under the age of 50; 35 percent are under 30.

But while 22.8 percent of Americans say they belong to no religion, only 3.1 percent are atheists and 4 percent are agnostic. The other 15.8 percent simply say that they belong to "nothing in particular."

This last group appears to be alienated from much of society. They "don't vote, don't marry and don't have kids" at the same rate as other Americans, Mike Hout, a sociologist and demographer at New York University, told Religion News Service. Only 37 percent of nones are married.

Some experts believe that the increase in nones is not as stark as it first appears. In the past, many people who had abandoned religion would have continued to identify with their birth religion, but today, the same type of person feels freer to say "none." These experts say that the culture has changed rather than people. It is now easier for people to say "none" than it was in the past. Whether it is culture or people or a mix, the impact on American society is great.

The most hopeful news about the nones is that 30 percent of them say that religion is at least somewhat important to them. We should also remember that in the 2009 Pew study, roughly a third of the nones said they "just have not found the right religion yet." These nones appear to be open to the possibility of returning to religion.

A lot of speculation has gone on about why the number of nones has increased. For answers, we can look back at Pew's 2009 study, "Faith in Flux."

The study found that nones have a very negative view of religion. About three-quarters of those who became unaffiliated said:

"Religious people tend to be hypocritical and judgmental rather than sincere and forgiving."

"Many religions are partly true, none completely true."

Religious organizations "are too focused on rules, not spirituality."

Likewise, the Public Religion Research Institute found that 70 percent of millennials say "religious groups are alienating young adults by being too judgmental on gay and lesbian issues,” while around 31 percent of millennials who left their childhood religion said "negative teachings about or treatment of gay and lesbian people” was important to their decision to leave.

According to the Pew study, about 65 percent of nones also said that religious leaders "want money/power, not truth/spirituality."

At the same time, 71 percent say that they "just gradually drifted away from the faith" and "stopped believing its teachings" (65 percent).

Some who grew up in unaffiliated families do turn to religion. Of those who were raised unaffiliated but joined a religion, 51 percent said that they became part of a religious group because their "spiritual needs were not being met." Religious services are very important for these converts: 74 percent say that they enjoy the religious service and style of worship of their new religion. A quarter said they had married someone of that faith.

Pope Francis appears to have intuitively understood the nones better than most religious leaders. His style is sincere and forgiving rather than hypocritical and judgmental. He has focused on compassion, spirituality, and concern for the poor, not on rules. He has preached that leadership is for service, not for power and money. While he has not changed doctrine, he shows an openness to discussion and the views of others.

Can Francis lead the nones to take another look at Christianity? If he can't, I don't think anyone can. But Catholicism is not just the pope; it is a community of believers who have to live the Gospel in a way that attracts rather than repels the unaffiliated. It has to be welcoming with worship services that are attractive, and it has to offer a spirituality that meets the needs of its people.

If people come back to church because of Francis but find a communities and clergy that are judgmental rather than compassionate, all about rules rather than love, they will head for the exit and never return.

*Correction: Original story incorrectly said that 13% of Catholics had left the church; should have been 13% of U.S. population are ex-Catholics. About one third of people who were raised Catholic have left the church.

[Jesuit Fr. Thomas Reese is a senior analyst for NCR and author of Inside the Vatican: The Politics and Organization of the Catholic Church. His email address is treesesj@ncronline.org. Follow him on Twitter: @ThomasReeseSJ.]